package com.gagakuai.bpm.utils;

import java.util.concurrent.CountDownLatch;

/*
 * @program: bpm_server
 * @description: id
 * @author: houhong
 * @create: 2022-06-20 09:39
 */
public class IDgenerateUtils {

    /*
     * 起始的时间戳
     */
    private final static long START_STMP = 1480166465631L;

    /*
     * 每一部分占用的位数
     */
    //序列号占用的位数
    private final static long SEQUENCE_BIT = 12;
    //机器标识占用的位数
    private final static long MACHINE_BIT = 5;
    //数据中心占用的位数
    private final static long DATACENTER_BIT = 5;

    /*
     * 每一部分的最大值
     */
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    /*
     * 每一部分向左的位移
     */
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

    //数据中心
    private static long datacenterId;
    //机器标识
    private static long machineId;
    //序列号
    private static long sequence = 0L;
    //上一次时间戳
    private static long lastStmp = -1L;

    public IDgenerateUtils(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }


    public static synchronized String nextIdStr() {


        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }

        if (currStmp == lastStmp) {
            //相同毫秒内，序列号自增
            sequence = (sequence + 1) & MAX_SEQUENCE;
            //同一毫秒的序列数已经达到最大
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            //不同毫秒内，序列号置为0
            sequence = 0L;
        }

        lastStmp = currStmp;

        Long nextId =  (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
                | datacenterId << DATACENTER_LEFT       //数据中心部分
                | machineId << MACHINE_LEFT             //机器标识部分
                | sequence;

        return nextId + "";

    }

    /*
     * 产生下一个ID
     *
     * @return
     */
    public static synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }

        if (currStmp == lastStmp) {
            //相同毫秒内，序列号自增
            sequence = (sequence + 1) & MAX_SEQUENCE;
            //同一毫秒的序列数已经达到最大
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            //不同毫秒内，序列号置为0
            sequence = 0L;
        }

        lastStmp = currStmp;

        return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
                | datacenterId << DATACENTER_LEFT       //数据中心部分
                | machineId << MACHINE_LEFT             //机器标识部分
                | sequence;                             //序列号部分
    }

    private static long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }

    private static long getNewstmp() {
        return System.currentTimeMillis();
    }

    private static CountDownLatch downLatch = new CountDownLatch(1);
    public static void main(String[] args) {
        /*  SnowFlake snowFlake = new SnowFlake(2, 3);


         */

        for (int i = 0; i <10; i++) {

                new Thread(new Runnable() {
                    @Override
                    public void run() {

                        try {
                            downLatch.await();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                        for (int i = 0; i < (1 << 2); i++) {
                            System.out.println(IDgenerateUtils.nextIdStr());
                        }
                    }
                }).start();

        }

        downLatch.countDown();
    }


}